If it's sciatica, I've found that what helps is good physical therapy and just time and more time. You might have to wait it out but eventually it will probably get better.

In the meantime you can go easy on the bad leg whenever possible. If you're standing at the kitchen sink, for instance, put that foot up on the shelf ledge if you have one under the sink--to relieve the pressure on the leg. It's more comfortable that way.

If you've been doing something--like standing or walking--for too long and the leg is acting up with pain, it's time to stop and rest. Maybe you'll need to rest for hours, maybe for the rest of the day, or maybe just for a short time. If you keep on doing your activities with rest breaks in mind, you may find that the pain will get better even if it's only a gradual improvement.

Some physical therapists use ultrasound and electrostim to improve the situation, and I've found that those help too.